A known gas sensor detects a particular component (gas targeted for detection) contained in gas to be measured. The gas sensor includes, for example, a sensor element having a plurality of electrode terminal portions, a plurality of metal terminals electrically connected to the respective electrode terminal portions of the sensor element, a plurality of signal wires electrically connected to the respective metal terminals and forming signal paths for connecting the electrode terminal portions and external equipment, and a terminal insulation member for electrically insulating the metal terminals in contact with the respective electrode terminal portions from one another. The electrode terminal portions are provided so as to output a detection signal indicative of the result of detection of detection target gas to the external equipment or to receive current or voltage from the external equipment.
The terminal insulation member provided in such a gas sensor is not limited to one formed of a single member, but a terminal insulation member composed of a plurality of members is proposed. Specifically, a proposed terminal insulation member electrically insulating the metal terminals from one another has a structure in which a first holder (40), a second holder (50), and an external connector (20) are assembled together (see Japanese Patent Application Laid-Open (kokai) No. 2002-323470).